CREATE TABLE CUSTOMER (
CUSTOMER_ID NUMBER NOT NULL ,
"NAME" VARCHAR(50) NOT NULL,
ADDRESS VARCHAR(250) NOT NULL,
CREATED_DATE Date NOT NULL
);

create sequence AUTO_INCREMENT
start with 1 
increment by 1 
nomaxvalue; 

create trigger ID_INC 
before insert on CUSTOMER
for each row
begin
select AUTO_INCREMENT.nextval into :new.CUSTOMER_ID from dual;
end;